To my understanding we're going to be fighting groups of mobs instead of just one or 2 at a time like in wow. That in itself I think makes pulling too many mobs and therefore dying more likely than if we'd be fighting just one at a time. I don't have any problem with the game being challenging on lower levels too, just as long as it's not so hard people will ragequit and log to wow questing for easymode.
None of us is going to make it out this shit alive, so try to enjoy it while you can.
I assume it will be similar to the first Guild wars, which also had companions. Mobs were always in groups there, too an pulling 2 groups was sometimes doable (especially later in the game) but you had to really focus fire on the healers. I hope they make a shortcut to let your companions change targets, like they did in GW.
Not really its more about killing than collecting, and most are bonus quests which you dont have to pick up or hand in. They are given to you automatically in certain areas (normally areas you are going thru anyway for your story quests)...and once you do them they automatically complete and you get the xp for them.